cam ppt for lectures and tutorials

1. 1
Cams
• Cams are used to convert rotary motion to
oscillatory motion (almost always) or oscillatory
motion to rotary motion (rarely)
• For high speed applications – example, internal
combustion engines
• Objectives of this chapter:
– Learn fundamental concepts and terminology
– Learn how to design a cam and follower set to achieve
a desired output motion.

2. 2
Cam types
Plate cam
Wedge cam
Barrel cam
Face cam
θ θ
θ θ
y
y
y
y

3. 3
Followers
• Knife-edge
• Flat-face
• Roller
• Sperical-face

4. 4
Displacement diagrams
• Cam-follower: usually 1-DOF system
rise dwell return dwell θ
y

5. 5
Displacement diagram types
• Uniform motion,
– Constant velocity
– Problem: infinity acceleration at point where
dwell portion starts
• Parabolic-uniform
– Can be shown that acceleration is constant
• Sinusoidal (simple harmonic motion)
• Cycloidal

6. 6
Cycloidal displacement diagram

7. 7
Graphical layout of cam profiles
• Terminology
– Trace point: on follower; point of fictitious knife-edge
follower. Center of roller, surface of flat-faced
follower.
• Pitch curve
– Locus generated by trace point as follower moves
relative to cam
• Prime circle
– Smallest circle that can be drawn with center at the cam
rotation axis and is tangent to the pitch circle
• Base circle
– Smallest circle centered on cam rotation axis and is
tangent to the cam surface

8. 8
Layout of cam profile: roller follower

9. 9
Constructing cam profile:
kinematic inversion principle
• Consider that cam is stationary and that
follower rotates in the opposite direction
than the cam does in reality

10. 10

11. 11

12. 12
SVAJ diagrams: show displacement, velocity, acceleration versus θ